The development of new technologies and tools for the rapid toxicological profiling of chemical/pharmaceutical substances, at cellular levels, are of great need to reduce and refine the use of animals in research. Vascular cells control the permeability of blood vessels, inflammation and immunity, cell growth, among other key functions, which have an important impact in the homeostasis of the human being.
Vascular cells derived from human pluripotent stem cells (hPSCs) represent a potential cell source for vascular kits1, 2. The use of “embryonic” ECs may represent an opportunity to screen toxicity of compounds that affect embryonic vasculature. ECs have been derived from human embryonic stem cells (hESCs) using several methodologies such as embryoid bodies (EBs) which recapitulates in vivo embryogenesis3, 4, a mixture of EBs with 2D or 3D culture systems1, 5-7 and co-culture with cell lines8-10.
However, there is no report showing the specification of hESC-derived ECs into arterial, venous or lymphatic sub-phenotypes either in vitro or after transplantation in animal models. This is important for the development of vascular kits to assess vascular toxicity and to target specific vascular vessels for therapeutic use. During embryonic development, specification into arterial-, venous- or lymphatic-derived ECs is defined at gene level and is mediated by several signaling pathways including VEGF, Notch and ephrin before circulation begins11, 12. Studies in mouse have shown that ephrin B2 and its receptor ephB4 are differentially expressed in arterial and venous ECs, respectively, before the onset of circulation in the developing embryo13. After the onset of the circulation, the distinct hemodynamic forces found in arteries and veins, such as blood flow rate, direction and pressure, can be a major driver in the specification and maturation of the ECs11, 12. Indeed, hemodynamic forces as shear stress have the capacity to program or redirect the specification of blood vessel type during development11, 12.
The development of vascular kits requires the development of microfluidic platforms to screen multiple compounds in a high-throughput while the cells are exposed to shear stress forces typically found in vivo. Only recently, researchers have replicated the circular cross-section of blood vessels in microfluidic devices14-16. However, so far, these tools have not been used in the context of drug screening/toxicology assessment.